This application claims the priority of Japanese Patent Application No. 10-87959 filed on Mar. 16, 1998, which is incorporated herein by reference.
The present invention relates to a sealed battery and a method of manufacturing the sealed battery.
Sealing of a battery for preventing leakage of the electrolyte solution and protecting a water reactive active material used therein is conventionally conducted by placing a sealing material on the opening of the housing of the battery, and melting and then cooling the sealing material thereon.
In this sealing process, when the opening of the battery requires prevention of a short-circuit, a sealing material with an electrical insulating property is particularly used.
Therefore, any of electrical insulating materials, such as polyethylene and polypropylene, that can be adhered to the housing when thermally molten by heat applied for sealing was used as the conventional sealing material.
However, such a conventional heat-melting adhesive sealing material can easily flow out of the opening during the sealing process, and hence, the sealing tends to be incomplete. Such incomplete sealing can result in leakage of the electrolyte solution and a short life of the battery. Also, in the case where the sealing material also serving as the electrical insulating material flows out, a short-circuit can be easily caused when the housing is slightly deformed by the sealing heat, resulting in decreasing the yield rate of batteries.
In consideration of the aforementioned conventional disadvantages, an object of the invention is providing a sealed battery with few defectives such as a sealing failure and a short-circuit and a method of manufacturing the sealed battery in a high yield rate.
The method of manufacturing a sealed battery of this invention comprises a step of forming an electrically insulating sealant S for sealing an opening by placing an electrical insulating sealing material C, including a first sealing material A that is molten by heat applied for sealing and a second sealing material B that is more difficult to soften by the heat applied for sealing than the first sealing material A, on the opening and by heating and successively cooling the electrical insulating sealing material C.
Alternatively, the sealed battery of this invention comprises an electrical insulating sealant S for sealing an opening, and the electrical insulating sealant S includes a first sealing material A that is molten by heat applied for sealing and a second sealing material B that is more difficult to soften by the heat applied for sealing than the first sealing material A.
In this manner, the invention provides a sealed battery with few defectives such as a sealing failure and a short-circuit and a method of manufacturing the sealed battery in a high yield rate.